Mrs. Manet Kaufmann of Silver Spring, Md., asks: I have grown a cotton plant from seed; it is about 3 feet tall and has bloomed three times and now has three little pods. I notice little white flying bugs on it so I sprayed it with malathion 50% E insecticide; there are still some bugs around and the leaves are turning yellow and dropping off. Can you give me any advice on how to care for it?

For control of white fly, which is apparently the pest on your cotton plant, try mixing 4 teaspoons of dishwashing detergent per gallon of water; shake the mixture well and put it in a sprayer that shoots a fine mist. Spray the undersides of the leaves as well as the top. Repeated applications will be necessary until you have killed flies as they hatch out of the eggs. It is advisable to keep the infested plant isolated from other plants so as not to spread the pest. For smaller plants, a forceful spray of warm water at the kitchen sink several days in a row will get rid of the eggs. Make a collar of aluminum foil or stiff paper to surround the stem of the plant so that soil will not be washed out of the pot.

Mrs. Dennis Calvarese of Mt. Rainier, Md., writes: I have a Ficus Beig. in a 10" pot about 3 1/2 feet tall. It is about four feet from an easterly window. The leaves turn yellow and die. I water the plant when the top 2 inches of soil is dry. Should I cut of the two leafless stalks?

The Ficus species should be kept evenly moist. When you water, water thoroughly, let the pot drain, and after half an hour pour off any water remaining in the saucer. Possible causes of the yellowing leaves are: Too little water so that none gets to the roots deep in the pot; too much water and poor drainage so that the soil at the bottom of the pot is constantly waterlogged; cold air drafts. You can cut back the leafless stalks to within a few inches of the soil, and as the days lengthen, with good care, new growth should develop.

Sandra Kaminsky of Silver Spring, Md., asks: I recently received a large Whitman fern. How often should I water it and how? How often should it be misted? How much sun should it have? How can I tell when it needs transplanting and what soil mix should I use?

The Whitman fern is a cultivar of the Boston fern; it is Nephrolepis exaltata 'Whitmanii'. A north window is an ideal location; locate it in shade during spring, summer and fall; it may have two hours daily of indirect sun in winter. There is no hard and fast rule about watering . You must develop a sense of the feel of the soil. Over-and under-watering both result in shedding of leaflets. If the plant is in a cly pot, you can water it by setting it in a sink or tub of water; remove it as soon as it is soaked, usually when the bubbling stops.

To increase the humidity it is desirable to set the pot on a pebble tray. During the winter you can mist it with a fine spray atomizer. Mist early in the morning, applying enough to moisten the fronds. Fluffy types such as 'Whitmanii' are sensitive to too much water on the fronds and should be misted only when the air is extremely dry. It will tolerate a potbound condition. When the rhizomes begin to extend over the edge of the pot and you can see that the soil is full of roots, it can be repotted in a loose, well drained mix; a packaged general purpose potting soil mixed half and half with peat moss or leaf mold is suitable. Feed your fern twice yearly, in early spring and midsummer with standard house plant fertilizer diluted to half the strength recommended on the package label.

Mrs. S. P. Alden of Wheaton writes: I have started an avocado seed, which is still in the glass with water. It has developed a good root system and is sprouting at the top. What is the next thing for me to do to transplant it into a pot?

After several leaves have formed on the avocado sprout and roots almost fill the glass or jar, plant the seed in an 8 or 10 inch pot. Place gravel or pieces of broken pot in the bottom for drainage; use any general purpose potting soil. Leave half the seed above the soil surface. Water it well and place it in full sun. When it is about a foot tall, tie it to a stake. If you want it to branch, rather than to grow as a long, lean trunk, which it will soon do, pinch or cut out the top when the plant has reached a height where you would like for it to start branching - at about 2 feet possibly.

Marge Mahany of Bethesda writes: We have a hibiscus tree in a corner, with southern exposure, a warm, shaded, dry setting. I run a vaporizer in that room during the day to add moisture. Yellowed leaves keep occurring. If I don't water it, leaves droop; if I do, leaves turn yellow and fall off. Please advise.

This sounds like a watering problem. Hisbiscus needs as much sun and light as is possible, with liberal watering and syringing but good drainage. When the temperature is low, watering must be descreased, otherwise the roots will be damaged and leaves will yellow and drop. Hibiscus flourishes in a temperature between about 60 and 78 degrees. Be sure that when you water the plant you do a thorough job so that the total root ball is benefitted. Discard water that remains the saucer after 15 minutes.

Mrs. W. R. Foster of Bethesda asks: What kind of begonia is this (sample enclosed). It was given to me as a rooted cutting six months ago, with the name 'Dancing Lady." It keeps growing new leaves but is dropping the old ones. Why? I have tried it in both north and west windows, and have tried more water and less water. Nothing works.

The specimen received in the mail was badly deteriorated. There is a begonia called "Dancing Girl," which may be the one you have. It bears a resemblance to the angel-wing type begonia, but no two leaves are alike in shape and size. Some of Dancing Girl's leaves are green with silver spots, others almost completely covered with silver. The flowers are white. Conditions which cause begonia to lose leaves are: A chill draft; air is too dry; too much water too often; insect pests; dormancy. I would guess dormancy is the situation in your case; many begonias "rest" in fall and winter.